Methods of packaging with films include, for example, household wrap packaging, twist packaging, sack packaging, skin packaging, shrink packaging, stretch packaging, and the like. Among them, since the shrink packaging can package tightly the articles to be packaged and can enhance the commercial value of packages, this method is suitably used for packaging of foods, miscellaneous goods, etc. Heat shrinkable films used for the shrink packaging are required to have the following characteristics: (1) they can tightly finish the package without causing deformation of the articles to be packaged; (2) they are low in haze and high in gloss, and can finish the package with beautiful appearance of contents; (3) they are not hazed with water droplets in refrigeration and are superior in visibility of the contents; and others.
In addition, for continuous shrink packaging of a plurality of articles, in general, the articles are primarily packaged by pillow packaging or overlap packaging with leaving some allowance between the film and the article, and then the packaged articles are passed through a heat shrink tunnel to heat shrink the film.
Recently, packaging by continuous packaging machines has been speeded up, and hence, the characteristic required for heat shrinkable films used for the packaging have become severer. Main characteristics required for heat shrinkable films used on continuous packaging machines are as follows:                (4) With speeding-up of continuous packaging machines, the films must be superior in slipperiness between the machines and the films.        (5) They must have hot tack sealing strength to perform firm sealing in a short time.        
As heat shrinkable films, there are known multi-layer films comprising various ethylene polymers. For example, JP-A-5-131599 discloses a polyethylene heat shrinkable laminate film excellent in adaptability to packaging machines which contains in inner, outer and intermediate layers a linear low density polyethylene specified in density and melt index.
Furthermore, JP-A-5-105787 discloses a resin composition for films which comprises a mixed resin of a linear low density polyethylene and a low density ethylene-α-olefin copolymer specified in melt index to which a specific amount of an anti-fogging agent is added.
On the other hand, JP-A-6-106668 discloses a cross-linked film comprising an ethylene polymer resin having proper heat shrinkage, heat shrinkage stress and tear strength and excellent in transparency.
However, these films have the following problems.
The film disclosed in JP-A-5-131599 is excellent in sealability, but inferior in heat resistance, and the temperature of heat shrink tunnel or heat sealing temperature cannot be high. For these reasons, the film has a restriction in packaging conditions for performing high-speed packaging.
AS for the film disclosed in JP-A-5-105787, enhancement of fog resistance is aimed at by improving bleeding-out of surface active agent, but no sufficient fog resistance has been obtained. Moreover, since this film is cross-linked, raising of heat sealing temperature is apt to cause failure in sealing due to fusion bonding of the film to a sealing bar or extension of sealed portions. Therefore, this film cannot be applied to high-speed continuous packaging machines.
The film disclosed in JP-A-6-106668 is a cross-linked and stretched film, and hence, is improved in heat resistance and has proper heat shrinkage and heat shrinkage stress, and further is good in sealability. However, since the film is insufficient in slipperiness, it is apt to be broken when the continuous packaging machine is operated at high speed. In addition, the film is insufficient in fog resistance.
The object of the present invention is to provide a heat shrinkable film which satisfies characteristics to be adapted for speeding-up of continuous packaging machines, namely, proper coefficient of dynamic friction and hot tack sealability with keeping heat shrink characteristics and appearance after shrinking, such as fog resistance and gloss.